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I have been having a difficult time starting my 912ul. I have read a couple of similar posts without a definite resolution.
I have a new battery and get good crank speeds. I need to use 3 5-10 second cranks to get it to fire and then it runs fine and will start first crank until then next cold start. Third time is always a charm. Never one, never two always three sometimes four if over a week. Carbs have been rebuilt and synchronized. I always use premium fuel without ethanol.

Any and all advise is much appreciated.
  • Re: hard start

    by » 9 years ago


    Hi Tim,

    Do you have the choke (enricher) hooked up or use a primer setup? Not using the choke and throttle correctly will cause hard starting. Having a high idle and using the choke with some throttle will cause too rich a mixture and hard starting. Having too low an idle rpm and no throttle may cause hard starting. What is your starting procedure? If you live in cold weather country and the engine is too cold it will be hard to start.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell


  • Re: hard start

    by » 9 years ago


    Thanks for your reply. I have a choke setup. The idle is to run at 1800 and I have the throttle closed when starting. I have tried opening the throttle a crack but no improvement which runs with your logic. I live in a cold climate but have had issues all summer.
    I did have the idle set up higher last fall as it was set to around 1200, much to low. I do not smell fuel so I doubt that it is flooding and it never behaves as such. What puzzles me is how consistently it starts after the third try.
    I may try to set the idle down to 1600. Any other suggestions?

  • Re: hard start

    by » 9 years ago


    One more thing that works is to re-gap your plugs to the min 0.6mm (0.023"). Good old Roger always recommends this... except this time.

  • Re: hard start

    by » 9 years ago


    Thanks I will try this first as they are presently gapped to .7mm
    The spark plugs can tell quite a story, do you have any tips on reading the rotax 912 plugs

  • Re: hard start

    by » 9 years ago


    Hi Rob,

    Good catch and observation that I was asleep at the wheel. Wonder if I can blame it on my dog. LOL

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell


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